关键词: 致密, 砂砾岩, 储层, 孔隙结构, 物性, 徐家围子

Abstract: In order to provide basis for reservoir prediction, the characteristics of nanometer-micron pore throat in dense conglomerate reservoir and its relationship with physical properties and productivity are discussed. Through thin slice observation, scanning electron microscope, high pressure mercury pressure, constant speed mercury pressure and physical properties test, a systematic analysis of reservoir space types, pore throat distribution, connectivity and physical properties is carried out. The results show that the pore types including dissolved pores, intercrystalline pores, primary intergranular pores, microcracks,with the feldspar solution pores and debris solution pores have the greatest contribution to porosity, followed by intercrystalline pores of clay minerals. The distribution shape of pore throat is bimodal, and the radius of most pore throat is less than 1 μm. The pore is connected by few large throat and micro-fracture, resulting in poor correspondence between porosity and permeability. Comprehensive analysis of pore size classification, reservoir physical properties and reservoir productivity shows that pore types have a controlling effect on reservoir physical properties and productivity. The porosity and permeability, gas content and productivity of reservoirs are lower when more capillary and microcapillary are developed in the pores. This explains the difference between the exploration efficiency of relatively high porosity reservoirs and relatively low porosity reservoirs. Geological conditions for the development of nanocapillary and microcapillary are discussed. It is suggested that the prediction of sedimentary facies and the study of diagenetic facies should be strengthened in reservoir prediction.

Key words: Tight, Sandy conglomerage, Reservoir, Pore structure, Reservoir physical property, Xujiaweizi area